Clay Minerals, Paleochemistry and Diagenesis in Rift-Lake Environments

该项目将涉及对最近从东非马拉维湖和图尔卡纳湖收集的许多长沉积物岩心（长达12米）中的粘土矿物进行详细的矿物学和化学分析。通过仔细分析粘土组合的垂直变化，并将这些变化与硅藻含量、物理地层学和间水化学的变化联系起来，我们将a)记录这些湖泊在过去几千年中古盐度波动的时间和程度；b)研究碱性湖泊中粘土矿物成岩的详细过程。特别是在不同的化学条件下，蒙脱石相中Mg的吸收和蒙脱石向伊利石的转变。这些数据将与来自这些湖泊流域的其他代用气候指标以及东非其他地方的先前研究相关联，以帮助记录全新世全球气候变化的模式。此外，由于裂谷和碱性湖泊现在被认为是地质记录中重要的沉积环境，因此了解这些现代环境中粘土矿物的行为将有助于评估非海相环境中埋藏成岩反应对石油生成和运移的作用。

This project will involve a detailed mineralogical and chemical analysis of the clay minerals in numerous long sediment-cores (up to 12m in length) which have been collected recently from Lake Malawi and Lake Turkana in East Africa. By analyzing carefully the vertical changes in the clay assemblages and correlating these with changes in diatom contents, physical stratigraphy and interstitial-water chemistry, we will a) document the timing and degree of paleosalinity fluctuations of these lakes during the last several thousand years and b) examine the detailed processes of clay-mineral diagenesis in alkaline lakes, especially the uptake of Mg in smectite phases and the transformation of smectite into illite under variable chemical conditions. The data will be correlated with other proxy climatic indicators from these lake basins and with previous studies elsewhere in East Africa to help document patterns of global climate change in the Holocene. Furthermore, since both rift-valleys and alkaline lakes are now recognized as important depositional environments in the geological record, an understanding of the behavior of clay minerals in these modern settings will help evaluate the role of burial diagenetic reactions for the generation and migration of petroleum in non-marine settings.